The invention relates to an additional outfit of sewing machines for sewing together two workpiece parts by means of a bead seam as presented in the pending patent application Ser. No. 875,417, filed Feb. 6, 1978. This type of machine is suited for joining workpiece parts by means of a bead seam, at which ruffling may become necessary, too, e.g. at moccasin shoe parts. In order to provide a fluid-tight connection of the two workpieces, the bead itself of such a produced beam seam is strongly marked by the fastened stitch formation.
In opposite to this type of moccasin shoe provided with a strongly marked beam seam, there is another type of moccasin shoe provided with a flattened less marked bead seam on the market, accordingly to fashion's demand. The operation of bead seam flattening takes place while the steam-treated shoe upper is pulled over the shoe last and the beam seam is stretched to a flat configuration. In order to allow this flattening, an additional amount of thread of each stitch is required and obviously such a moccasin shoe does not have the aforesaid fluid-tightness.
As described in the above cited pending patent application, the conventional method of making moccasin shoes by hand is very expensive and time consuming. Now, with the additional requirements of providing an additional amount of thread to each stitch, this manual procedure becomes even more complicated and hardly to perform. The main problem presents the provision of an equal amount of thread to each stitch, in order to achieve an uniformly flattened bead seam having an equalized strength.